[Rack] Electric door strike working again. Use your Pin or key to get in.

Jake jake at spaz.org
Mon Jul 15 09:24:43 UTC 2013

what I installed is a small motor with a long shaft, and there's a string 
(actually the reinforcement from a fiber optic cable) that wraps around 
the shaft and goes to the indoor lever on the gate latch.

So when the motor shaft turns, it wraps string around its shaft and pulls 
the string, which tilts the lever over as if a fleshbag is trying to open 
the door from the inside with their meat thumbs.

unfortunately the motor i chose is not powerful enough with 24v, so we 
need to either give it 36v and see that it is good, or do something else 
like replace the motor.

we could also try using the green plastic gear that the motor is geared 
to, which would give it more leverage.  But someone would have to glue a 
disc onto the side of the gear to turn it into a pulley, and attach the 
string to it so it could get wound up onto it.

come on hackers, hack already!  jeez.

On Mon, 15 Jul 2013, Jonathan Lassoff wrote:

> Yeah, so what's the new motor? I haven't been by in a few days. 
> Is this just another buzzer, or some kind of rotationally-driven mechanical actuation?
> Either way, sounds like some cool progress is being made. 
> Awesome!
> On Sunday, July 14, 2013, Henner Zeller wrote:
>       On 14 July 2013 20:53, Martin Bogomolni <martinbogo at gmail.com> wrote:
>       > Quick thing--
>       >
>       > Remember that Fire Code requires that any electric door strike, or
>       > magnetic strike, must allow someone to leave without being impeded in
>       > a panic.  On magnetic doors, this requires a panic push bar that
>       > physically breaks the electrical connection.   On mechanical electric
>       > strikes, this requires that either a pushbar or simple lever be
>       > pushed/rotated to bypass the electrical lock.
>       The regular lock will just work the way it is now - by rotating the lever.
>       -h
>       >
>       > -M
>       >
>       > On Sun, Jul 14, 2013 at 10:41 PM, Jake <jake at spaz.org> wrote:
>       >>> The motor Scotty found takes about 300mA at 6V when free-running (so
>       >>> for no-load 'return', maybe 500mA with load). It runs about 1 second
>       >>> for the amount of time we need. That is about 1.8 Joules.
>       >>> Say we can charge up a capacitor to 18 V (peak voltage of a bit more
>       >>> than 12 V AC) and drain it down to 4 V (when this particular motor
>       >>> just works), then we'd need about 20'000 microfarad ( 2 * 1.8 joules /
>       >>> ((18 - 4) volt)^2 ). The calculation would be similar for other
>       >>> motors found in the pile.
>       >>
>       >>
>       >> there are at least ten 1000 microfarad capacitors rated at 50 volts in the
>       >> pile, and i can certainly find more.  But i think the math is more
>       >> complicated.  But since it's based on voltage squared, one 50 volt 1000 uF
>       >> capacitor is the same energy as a 20,000 uF capacitor rated at 11.1 volts.
>       >>
>       >> anyway that motor sounds hella weak.  The motor i already mounted on the
>       >> door is rated 24 volts and probably can take a good amp or two at least,
>       >> which is a lot more power.
>       >>
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